The present invention relates to an optical scanning device in which a grating disc provided with a plurality of linear diffraction gratings in an annular arrangement deflects a laser beam in order to scan a desired plane by the deflected laser beam.
In an optical scanning device of the type described, it has been customary to configure each of the linear diffraction gratings relatively large so that the laser beam may undergo deflection which is great enough for optical scanning. The problem encountered with such prior art configuration of diffraction gratings is that the grating disc as a whole become bulky and the deflection rate of the laser beam is lowered.